Procedure for making a resilient foot-support



Jan- 4, 1956 T. E. INGERSOLL 3,227,795

PROCEDURE FOR MAKING A RESILIENT FOOT-SUPPORT Filed Feb. 28, 1962 ATTORN EY United States Patent O 3,227,795 PROCEDURE FOR MAKDIG A RESILTENT FOGT-SUPPORT Theo E. Ingersoll, 81S Oalrmere Drive, North Muskegon, Mich. Filed Feb. 28, 1962, Ser. No. 176,413 3 Claims. (Cl. 264-223) This invention relates to the preparation of a resilient support for a foot within a shoe. It is generally recognized that a persons weight is not normally transferred by the foot at a uniform distribution over the entire bottom area. The abnormal foot does not properly align the areas of weight transfer with the muscle and bone structure, resulting in extreme discomfort or disability. This structural misalignment of the foot can be compensated for in many cases by filling the voids between the foot and the sole of the shoe with a iiexible medium for transferring the weight with more uniform distribution, or by transferring it at selected areas to permit healing and realignment of the foot. The use of this technique is well known, and the more practical versions of it involve the use of a mixture of latex and a fibrous bulk material to produce a plastic dough-like mass which is inserted in the shoe and displaced by the foot prior to curing of the mass to permanent resilient condition.

A preservative of an alkaline nature is usually incorporated in latex, and the use of this additive is not carefully controlled. Setting of the liquid latex to resilient condition is generated by a catalyst which increases the acidity, and it is obvious that curing time will be a function of the balance between the acid catalyst and the alkaline preservative. One diiiiculty encountered in the conventional forms of the technique referred to above is the problem lof controlling curing time, because of the variations in acidity in the generally available supply of latex.

The eiiicient mixing of catalyst and latex by conventional procedures is a requirement met only with difficulty, when the small quantities required by a foot support are individually prepared for each use. This invention provides a procedure for assuring the proper mixture and control of the catalyst to produce the desired degree of acidity without requiring extensive effort or special equipment. The invention also provides a technique for preventing the adherence of the plastic mixture to the foot or stocking during the curing period, and yet permits the adhesion to develop between the support and the shoe structure, when this is desirable.

In the preparation of the principal ingredients of the foot support, it is recommended that standard techniques be applied to the latex and to the bulk material to determine the precise hydrogen ion concentration (pH) of each, which is the conventional designation for the acidity-alkalinity condition. The amount of acidification necessary to produce a desired setting time is then determined from generally available reference material, and it is preferable that this acidification be obtained from an acid powder such as tannic acid, salicyclic acid, or some equivalent composition of comparable hydrogen ion concentration.

A bulk material such as ground cork, leather dust, flocking compound, ground rubber, wood our, or other generally available substance of a similar nature, is mixed with sufficient acid catalyst to provide the particular liber with the proper predetermined acidity for a particular latex batch. It is important to note that the acidifying catalyst is added to the bulk material, and mixed intimately with it prior to the addition of the latex. This results in a thorough dispersion of the catalyst, with the result that the later addition of the latex liquid is much "ice less likely to encounter quantities of increased concentration of the catalyst, and therefore less mixing eiiort and mixing time is required. This procedure also permits packaging of the catalyst-bulk in a premixed condition for use with certain latex.

When a particular foot-support is to be prepared, the acidiiied bulk material is preferably mixed in a ratio of approximately three volumes of bulk material to one of latex, and kneaded together for sixty seconds to provide the proper density for the molding operations. As an aid in approximating the minimum quantity to be prepared for basic molded supports, it is suggested that the following rule of thumb be used:

(a) Double the shoe size to determine the number of tablespoons full of bulk material for a pair of rear foot molds.

(b) Triple the shoe size to determine the number of tablespoons full of bulk material for constructing a pair of full foot molds.

(c) For children sizes l to 11, use six tablespoons full of the bulk material; and for sizes 111/2 to 3 (a change in the range of conventional number sizes occurs here), use nine tablespoons full of the bulk material.

Tackiness of the resulting mass, one of the necessary though objectionable features of molding compounds in the past, has been controlled and actually used as a benecial factor by this invention. Conventional types of dynamic molding materials required envelopes or coverings to contain the mass while setting. These coverings Were necessary to prevent bonding of the tacky mass to the stockinged feet of the wearer and to prevent extrusion of the soft mass (which was lacking in a predetermined setting factor) from the shoes. This tackiness is used by the preferred procedure of this invention to maintain the fixed position of the mass in the shoes while the setting process takes place, and to further retain adhesion of the mass to the shoes during the curing period (which is usually three weeks, to eliminate shrinkage in the iinished support). At the same time easy removal of the supports from the shoes is possible because of the peculiar characteristics 4of the mass when completely cured.

Tackiness is useful in certain areas, as outlined above, but is undesirable elsewhere. Another feature of this invention concerns the use of a second catalyst in the proce-ss to control tackiness and to trigger the setting process into immediate action. An acid separator is sprayed or dusted over preferably the top surface only of the prepared support mass immediately prior to placing the feet into the shoes to induce a quick setting of the surface layer of the mass to form a sheath or envelope-like covering. This thin sheath loses all of its tackiness by sudden curing through the chemical reaction of the mass with the separator, thereby eliminating any tendency to adhere to the stockings of the wearer. The cured skin further provides an extremely pliable envelope enabling continu-ation of dynamic moulding by permitting the feet to displace the still moldable material contained thereunder while walking. The preferred separator is a 7% acetic acid solution, which is a weak acid, applied -as a spray. Normally, the accelerator spray will meisten the side areas of the mass also, and will thereby prevent adherence of the support to the side structure of the shoe. This will permit a spatula to be inserted between the Isupport and the shoe sole for removal of the support later for correction or alteration. If desired, the entire outer surface of the inserted mass of uncured plastic material may be moistened with the accelerator to prevent adherence at all places, and thus facilitate an expected removal for addition or modification. The quantity of the accelerator spray may be increased also to the point of providing a sufficient quantity of acid to penetrate into the mass to some degree to produce at least an initial set to supplement the effect of the catalyst previously incorporated in the bulk material. The quantity of catalyst incorporated in the bulk material, together with the accelerator spray, should normally be selected to produce a full setting of the latex within approximately five minutes after walking has commenced, during which time the weight of the wearer causes the plastic material to flow to its desired ultimate position. Settingj as used in this discussion, refers to the disappearance of flowable plasticity, while curing refers to the development of full strength and resiliency. The mix as initially prepared can be adjusted by the addition of tragacanth gum acacia, or other thickeners, with wetting agents such as soap solutions, or with soybean oil or mineral oil as a thinning material. The various bulk materials will exhibit different degrees of surface tension and viscosity influences, and these must be compensated for by the above adjustments to produce the best molding material.

There are several incidental advantages to the procedure outlined above, one of these being that the mass is completely self-vulcanizing and requires no adhesive to maintain its position within the shoe. A freshly compounded mass of plastic can be added to an existing shoe support either in the wet or dry stage, regardless of whether or not the accelerating spray has been used. The support may be removed from the shoe, and may be ground with sanding discs or other such equipment, and may be cut and trimmed with knives or scissors. In this manner, a progressive alteration to the position of the foot may be developed as a means of orthopedic correction.

The procedure for making a foot-support from the material prepared as outlined above is illustrated in the accompanying drawing, in which:

FIGURE 1 is a schematic view of a shoe prior to the insertion of the plastic material therein.

FIGURE 2 illustrates the same shoe with a quantity of the uncured plastic material positioned preparatory to the insertion of the foot.

FIGURE 3 illustrates the condition of the shoe after the foot has been inserted, showing the manner in which the plastic has been displaced by the foot so that it occupies the spaces between the structure of the shoe and the contour of the foot.

Referring to FIGURE 1, a shoe generally indicated at 10, is presented in schematic form, no attempt being made at a detailed representation of the shoe structure. The shoe may be regarded as including the upper portion 11, the sole 12, the heel 13, and the insole 14. FIGURE 2 indicates the insertion of a quantity of uncured plastic material within the shoe preparatory to the insertion of the foot 16, which is illustrated in position in the shoe in FIGURE 3. The insertion of the foot deforms the material, 15, so that it occupies the spaces between the insole 14, and the bottom of the foot 16. If desired, the quantity of material 15, may be adjusted so that it will occupy the space 17, between the upper part of the foot and portions of the upper portion 11 of the shoe. The curing of the plastic material 15 to stress-resisting condition with the weight removed from the foot 16, results in continuity of the cured supporting member because of the removal of a tendency to completely squeeze out the plastic material at portions 18 under the heel of the foot, and at similar portions of other parts of the foot which may vary due to the particular foot condition involved. Curing of the supporting member With weight removed also tends to maintain a more natural undistorted position of the foot so that the transfer of weight from the foot through the cured supporting member will take place with the foot in a more desirable condition. This arrangement is particularly advantageous where muscular weakness has resulted in inability of the foot to maintain its proper position unassisted when weight is placed upon it.

The particular embodiments of the present invention which have been illustrated and discussed herein are for illustrative purposes only, and are not to be considered as a limitation upon the scope of the appended claims. In these claims, it is my intent to claim the entire invention disclosed herein, except as I am limited by the prior art.

I claim:

1. A method of making a foot-support comprising:

mixing a quantity of bulk material with an amount of salicylic acid powder selected to establish a particular curing time for a particular amount of a liquid latex composition to form a mixture;

adding said mixture to said amount of liquid latex composition to produce a mass;

inserting a quantity of said mass in a shoe, and accelerating the curing of the exposed surface of the said mass with an accelerator liquid in the form of a weak acid to reduce adhesiveness of said surface and produce a cured skin on said mass;

inserting the foot of the wearer in the shoe thus prepared to position the said mass therein prior to cornpletion of curing.

2. A method of making a foot-support comprising:

mixing a quantity of bulk material with an amount of tannic acid powder selected to establish a particular curing time for a particular amount of liquid latex composition to form a mixture;

adding said mixture to said amount of liquid latex composition to produce a mass;

inserting a quantity of said mass in a shoe, and accelerating the curing of the exposed surface of the said mass with an accelerator liquid in the form of a weak acid to reduce adhesiveness of said surface and produce a cured skin on said mass;

and inserting the foot of the wearer in the shoe thus prepared to position the said mass therein prior to completion of the curing thereof.

3. A method of making a foot-support, comprising:

mixing a quantity of fibrous material with an amount of acid powder selected to establish a particular curing time for a particular amount of a liquid latex composition to form a mixture;

adding said mixture to said amount of liquid latex composition to produce a mass;

introducing a quantity of said mass in a shoe, and accelerating the curing of the exposed surface of the said mass with an accelerator liquid in the form of a weak acid to reduce adhesiveness of said surface and produce a cured skin on said mass;

and inserting the foot of the wearer in the shoe thus prepared to position the said mass therein prior to completion of curing.

References Cited by the Examiner UNITED STATES PATENTS 2,136,815 11/1938 Forster et al. 18-55.05 XR 2,163,986 6/1939 Shepherd 264-307 2,359,698 10/1944 Uhlig 264-307 2,565,758 8/1951 Covino 264-223 ALEXANDER H. BRODMERKEL, Primary Examiner.

WILLIAM STEPHENSON, Examin, 

1. A METHOD OF MAKING A FOOT-SUPPORT COMPRISING: MIXING A QUANTITY OF BULK MATERIAL WITH AN AMOUNT OF SALICYCLIC ACID POWDER SELECTED TO ESTABLISH A PARTICULAR CURING TIME FOR A PARTICULAR AMOUNT OF A LIQUID LATEX COMPOSITION TO FORM A MIXTURE; ADDING SAID MIXTURE TO SAID AMOUNT OF LIQUID LATEX COMPOSITION TO PRODUCE A MASS; INSERTING A QUANTITY OF SAID MASS IN A SHOE, AND ACCELERATING THE CURING OF THE EXPOSED SURFACE OF THE SAID MASS WITH AN ACCELERATOR LIQUID N THE FORM OF A WEAK ACID TO REDUCE ADHESIVENESS OF SAID SURFACE AND PRODUCE A CURED SKIN ON SAID MASS; INSERTING THE FOOT OF THE WEARER IN THE SHOE THUS PREPARED TO POSITION THE SAID MASS THEREIN PRIOR TO COMPLETION OF CURING. 